Clock circuit in Topstar P4M266 motherboard

Shown is the clock circuit in the Topstar P4M266 motherboard + this circuit is based on the large-scale integrated circuit ICS950901 as the core
.
    The working process of this circuit is:
    In the figure, U19 is the clock signal generator chip ICS950901, which has a total of 48 pins , among which XIN is the crystal oscillator input terminal. XOUT
is the output terminal of the crystal oscillator. These two pins are connected to the 14.3 MHz quartz crystal. The two pins of the crystal should have a voltage difference of about 0.4 V under normal conditions
: VCCCPU, VCCPCI, VCC48 and other pins are the power supply terminals. , its power supply voltage is 3,3 V (pin 1 of the A'IX power supply);
the SDATA pin and SCLK pin are serial data and serial clock respectively, provided by the south bridge chip; the VTT_PWRGD pin is the PG signal
Input terminal: PCICLK3 and PCICLK7 pins are PCI clock output terminals i 48 MHz/FS3 is 48 MH clock output.
    When the motherboard power-on button is pressed, the 3.3 V supply voltage of the AIX power supply is filtered by the inductor and capacitor and then sent to the power supply pin of the clock signal generator
chip U19 to supply power to the clock chip. After the CPU power supply is normal, the PG signal output is sent to The VIT PWRGD pin of U19,
and then the crystal oscillator inside the clock generator chip U19 starts to work, providing a
clock frequency of 14.318 MHz for the frequency multiplication, frequency division and other circuits in the U19 chip. This signal is processed in U19 to obtain clock frequencies of 33 MHz and 48 MHz after up-conversion and down-conversion. Then it is output through
the clock output pin , and then sent to each pin of the motherboard through the 22 n and 33 n current limiting resistors. component, providing it with a clock signal (operating
frequency).
    Some motherboards (generally referring to P4 and above motherboards) have two clock chips. One is a clock chip connected to the 14.318 MHz crystal, and
the other is located near the memory slot and is designed to provide clock signals for the memory slot and Northbridge chip. circuit.